JPH02299463A - Power supply device - Google Patents

Abstract

PURPOSE:To make it possible to control output voltage exceeding the breakdown voltage of a switching element by providing a voltage superposing means superposing the output of a transformer and a feedback control means controlling the duty of the switching element, and controlling ON and OFF operations of the switching element. CONSTITUTION:The time ratio of ON/OFF operations of a switching transistor Q1, that is, the duty is varied by a comparator Q3 comparing a feedback signal made by resistors R2 and R3 making the partial voltage of the first outside output end O1 with control value Ex, and voltage can be controlled by the second output T2 of a transformer T superposed to the first output T1 of the transformer T. According to the constitution, the output voltage exceeding the breakdown voltage of the switching transistor Q1 can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-output power supply device, particularly for copying machines, L
The present invention relates to a power supply device such as a BP (laser beam printer) that requires various low voltage and high voltage outputs.

(Conventional technology) Conventionally, power supplies that generate voltages with different generation timings are
It was common to use independent transformers and control circuits for each output.

There is also a method of using a transformer with multiple outputs, inserting a transistor on the low voltage side of the output to be controlled on the secondary side, and performing series control with this transistor, but since the transistor is used in an active state, there is a large loss, and the control The range was also limited to the withstand voltage of the transistor. Additionally, elements such as varistors were required to protect the transistors.

[Problems to be Solved by the Invention] Since the conventional example is configured as described above, it is difficult to reduce the cost and size of the device.

The present invention was made under these circumstances, and it is an object of the present invention to provide a power supply device that can be reduced in cost and size.

[Means to solve the problem]

In order to achieve the above object, the present invention configures a power supply device as shown in (1), (2), and (3) below.

(1) A capacitor and a resistor are connected in series between one end of the second output of a transformer having multiple outputs and one end of a switching element, and the other end of the switching element and the other end of the second output of the transformer are connected in series. A clamp diode is connected between the other end of the switching element and a common connection point of the capacitor and resistor or one end of the switching element, and a first terminal of the switching element and a first output of the transformer are connected. A power supply device having a voltage superimposition means connected between one end or the other end, and a feedback control means for controlling the duty of the switching element connected between the first output side of the transformer and a control terminal of the switching element. .

(2) In (1) above, the voltage superimposition means includes a diode whose one end is connected to one end of the first output of the transformer;
A power supply device comprising a capacitor connected between the other end of the diode and a first terminal of a switching element, and a diode connected to the other end of the diode to serve as a first external output terminal.

(3) In the power supply device according to (1) above, the voltage superimposition means includes a rectifier circuit connected between the first terminal of the switching element and the other end of the first output of the transformer.

(Function) With the configurations (1), (2), and (3) above, it is possible to control an output voltage higher than the withstand voltage of the switching element by turning the switching element on and off.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment of the present invention.

In the figure, the transformer T has at least two outputs, a first output T1 and a second output T2. The first output T1 is connected to the first external output 11I via diodes D1 and D2.
Connected to δ1. Further, the second output T2 is connected to the second external output l1lIoz via a diode D3.

In addition, the second output T2 is simultaneously connected to the capacitor CI and the resistor R.
1 to the switching transistor (switching element) Ql, and a clamp diode D4 is connected to the common connection point of C1 and R1. Also, R1 and Ql
A common connection point of is connected to a common connection point of the diodes D1 and D2 via a capacitor C2. Further, the first external output terminal 01 is smoothed by a capacitor C3,
The voltage is also divided by resistors R2 and R3, and a feedback signal is sent to a comparator (feedback control means) Q3.
The control value EX is also input to the other side of the comparator Q3, and the output terminal of the comparator Q3 is connected to the base (control terminal) of the switching transistor Q1. In addition, the primary side of the transformer T is connected to the DC power supply VCC and the switching transistor Q2.
is driven by a PWM (pulse width modulation) control circuit Q4. Capacitor C2 and diode D1 constitute voltage superimposition means for superimposing the first and second outputs of the transformer.

Note that the feedback signal IN to the PWM control circuit Q4
, may be, for example, a signal obtained by smoothing and dividing the output of the second external output terminal "62," or may be a signal obtained by dividing the output of the transformer T (
(not shown) may also be used.

Next, the operation of this embodiment will be explained. FIG. 2 shows the timing chart. Here, assume that the polarity of the secondary side of the transformer is determined so that when the diode D1 is on, the clamp diode D4 is on. When the primary side is driven by the PWM control circuit and the four switching transistors Q2, each output TI depends on the turns ratio, switching duty ratio, and transformer winding polarity.
, a pulse is generated at T2. This waveform is VTI, V7
Set it to 2. First, if the control value Ex is set to a value such that the switching transistor Q1 is always saturated, the diode D1 is turned on during the period when the clamp diode D4 is turned on, as described above, and V04. Ov is applied to vB, and the first output T1 is applied to vA, and the capacitor C2 is charged with the peak value of the first output T1 (this is referred to as vTl+). Also, at this time, diode D2 is turned on and capacitor C3 also has a voltage of V.
Tl' is charged. Next, during the period when the diode D1 is off and the clamp diode D4 is off, the second output T2
A current flows from the switching transistor Q1 through the elements C, , R, but since Ql is saturated, v8 is Ov, and vA is held at V71+ by the capacitor C2. As a result, the output of the first external output terminal 01 is V7
1 + roar (period (A) in Figure 2).

Now assume that the control value EX is set to a value at which the switching transistor Q1 is always cut off. At this time, the period during which the diode D1 is on is the period when the clamp diode D4
is also on, VD4=Ov, VB is also almost Ov, and v
The TI(7) output is applied to A, and the capacitor C2 is charged with the positive voltage peak value of the first output T1, and at the same time, the diode D2 is turned on and C3 is also set to V. . is charged.

Further, at this time, the capacitor C1 is charged with the negative peak value V〒2- of the second output T2. Next, during the period when the clamp diode D4 is off and the diode D1 is off, the switching transistor Q1 is off, so the second output T
The voltage obtained by superimposing the voltage vT□- charged on 01 on 2 is V
B, and as a result, vA increases as v8 increases, +
VT,” and the positive voltage peak value of the second output T2 is v
72", the peak value of VB is Va, -+VT□◆
Therefore, VA(De- value is V71" + VT2-
+ V72" te, diode D2 turns on and capacitor C3 has V71" + V72- + V72
゜ is charged and becomes the output of the first external output terminal d1. V
When A exceeds its peak and begins to drop, diode D2 turns off. Next, when VA decreases and the period when diode D1 is on and clamp diode D4 is on,
V o4; Va; OV, and capacitor C2
The first output TI is applied to VA=VTI+ and the positive peak value of T1 is charged again, but the first external output vA0
The output of 1 is vT-+V↑2-+V7. Since the voltage is +, the diode D2 remains off. Next, diode DI
, D4 is turned off, the capacitor C is turned off by the operation described above.
3 is again charged with vTl++va, -+Va, +. The above operation is repeated (period (B) in FIG. 2).

In this way, the switching transistor Q1 is turned on/off.
The off makes it possible to superimpose the second output T2 of the transformer on the first output T1 of the transformer.

Next, the control value E is the output value of the first external output terminal 61 when the switching transistor Q1 is completely on, and
Set the value to a desired value that is between the 31 output values when Ql is completely off. First, the switching transistor Q1 is turned off. Diode D1. D4
While T is on, the output 61 is the first output T as described above.
The peak value of I becomes Va, +. Next is the diode DI.

When D4 is turned off and v8 starts to rise according to the T2 waveform, Va = V, 2- + V T2te, vA
V becomes ``+VB'' and starts to rise at the same time, diode D2 turns on and capacitor C3 is charged with V71''+vB. Then, a feedback potential based on the voltage division ratio of the resistors R2 and R3 is input to the comparator Q3 and compared with the control value EX.

The output of the first external output terminal d1 increases, and as a result,
When the feedback potential exceeds the control value E, comparator Q3 is inverted and turns on switching transistor Q1. When Ql is turned on, vB becomes 0■, so VA
=Vt+"tona'), D2 is turned off. Next, during the period when diodes Di and D4 are on, C2 is charged with Va,' as described above. At this time, diode D2 is off. The output decreases by consuming current at the output of 01, and the comparator Q3 inverts again, turning off the switching transistor Q1.Then, the diodes DI, D
During the period when Q4 is off, switching transistor Q3 is further inverted and charges C3 until Ql is turned on. The above operation is repeated (period shown in FIG. 2 (C)).

As described above, the circuit of the embodiment operates to control the first external output terminal 01 to a desired value.

That is, the resistor R2 that divides the voltage of the first external output terminal d1,
A comparator Q3 that compares the feedback signal generated by R3 with a control value Ex changes the on/off duty ratio of the switching transistor Q1, and the second output of the transformer is superimposed on the first output T1 of the transformer.
The voltage can be controlled from the output T2. In addition, in FIG. 2, the VB waveform is expressed in a rounded manner for ease of understanding.

Moreover, the same operation can be obtained even if the clamp diode D4 is connected in parallel with the switching transistor Q1.

Incidentally, the load on the apparatus of this embodiment is the charging of the copying machine. In the case of corona charging, the first output T1 of the transformer is
Keep the voltage at about this level, set the superimposition valve from the second output T2 of the transformer to approximately Ov during standby, and print operation (
(copying operation), a voltage is superimposed from the second output T2 of the transformer to the first output.

Next, FIG. 3 shows a circuit diagram of a power supply device according to a second embodiment of the present invention.

Similar to the first embodiment, the transformer T has at least two outputs, a first output T1 and a second output T2, and the first output T1 is rectified by a diode D1 and smoothed by a capacitor C3. and output to the first external output terminal d1.

Further, the second output T2 is connected to the second external output terminal d2 via a diode D3. The second output is simultaneously connected via capacitor C1 and resistor R1 to the collector of switching transistor Q1, and the common connection point of elements C1 and R1 is connected to clamp diode D4. Further, the collector of the switching transistor Q1 is input to a voltage multiplier rectifier circuit composed of a capacitor and a diode. In this embodiment, the voltage is input to a double voltage rectifier circuit consisting of capacitors 04~C7° and diodes D5~D8, and the output of the double voltage rectifier circuit is passed through a resistor R4 to the first output T1.
connected to the low pressure side of the

Each output T1. Let the waveform generated at T2 be V↑In Vd2. First, when the switching transistor Q1 is completely on, va is always Ov, so VA=Ov, and the capacitor C3 is charged to the negative peak voltage vT1- of the first output TI (V+), and the first is output to the external output terminal δ1. Next, the operation when the switching transistor Q1 is always in the off state will be explained.

In the cycle when clamp diode D4 is on, VD4
=O, and VB=O, and the capacitor C1 is charged with the negative voltage vT2- of VA. Next, the cycle in which the clamp diode D4 is off is V D4'' V B =
V T2-"V72 and ft'), the diode D5 is on, that is, Vos"0, and the peak value, that is, the positive peak value of V72, is V72" across the capacitor C4. Va2- +
V T2+ is charged. Furthermore, in the next cycle when D4 is on, V. 4zvazO, D5&t turns off and becomes Vos= (VTR-+VT2), then D6 turns on, this voltage moves to capacitor C5, and Voe=
(VTR-+VTR) Two. Next, in the cycle in which D4 is off, D5 is turned on again, Vos=OV, and capacitor C4: V72- +vA.

to charge. At the same time, V os=-(V T2- +
Because of V T2), D7 is turned on, charge is transferred to capacitor C6, and V D? = (VTR-+VTR) Furthermore, when D4 turns on, V Dl+
=-(V T2-+ V T2) Tona Rutame, V o7
=(VT2- +VT2") (VT2- +
VT2''), charge moves to C7, and eventually V
A=-2X(V72- +VT2"), and V^ is the v p- of the pulse generated at the second output T2 of the transformer
The voltage will be twice that of p. After that, the first external output terminal d
By repeating the above-mentioned cycle, each capacitor is charged by the amount of charge reduced by 1, and vA is maintained at a substantially constant voltage.

Next, the control value E is set to a value that becomes an intermediate voltage between the output voltage of the first external output terminal 61 when the switching transistor Q1 is on and off. As in the first embodiment, the output of 01 is voltage-divided and level-shifted by resistors R2°R3 and R5, and then manually inputted to comparator Q3, and the control value E
It is compared with X. The comparator Q3 turns on the switching transistor Q1 when the feedback voltage <E, changes the on/off time ratio of the switching transistor Q1 as in the first embodiment, and outputs the first external output terminal d1. operates to obtain the desired output voltage value. In this way, the control range is the second output T2 of the transformer.
The voltage is twice as high as Vp-p.

Note that the same operation can be obtained even if the voltage doubler rectifier circuit of this embodiment is further modified into a triple voltage rectifier circuit or a quadruple voltage rectifier circuit.

Furthermore, the configurations of the first and second embodiments described above can be combined to form a three-output quadrance power supply device. This example is shown in FIGS. 4 and 5 as the third and fourth embodiments of the present invention. The difference between the third and fourth embodiments is the presence or absence of a circuit for the switching transistor Q, and whether or not this circuit is necessary is determined by the output accuracy of the third output terminal d3.

Furthermore, by considering the polarity of the transformer, the capacitor C7 of the second embodiment can be omitted. This example is shown in FIG. 6 as a fifth embodiment of the present invention. As shown in the figure, a negative voltage is generated at the first output T1 of the transformer in the cycle in which the clamp diode D4 is on. = 2X
(VT2-+Vy2'')=V^, and at this time, the first external output terminal 01 is vA+v〒1-, and the capacitor C3 is charged with its peak.

〔Effect of the invention〕

As described above, according to the present invention, by turning the switching element on and off, it is possible to control the output voltage that is higher than the withstand voltage of the switching element, and it is possible to reduce the cost and size of the power supply device.

[Brief explanation of drawings]

1 is a circuit diagram of a first embodiment of the present invention, FIG. 2 is a timing chart of the same embodiment, FIG. 3 is a circuit diagram of a second embodiment of the present invention, and FIG. 4 is a circuit diagram of a third embodiment of the present invention. Example circuit diagram, 5th
The figure is a circuit diagram of a fourth embodiment of the invention, and FIG. 6 is a circuit diagram of a fifth embodiment of the invention. T----Transformer TI----First output to the transformer T2---- Second output of the transformer CI, C2・
... Capacitor R1 ... Resistance

Claims (3)

[Claims] (1) A capacitor and a resistor are connected in series between one end of the second output of a transformer having multiple outputs and one end of a switching element, and the other end of the switching element and the other end of the second output of the transformer are connected in series. A clamp diode is connected between the other end of the switching element and a common connection point of the capacitor and resistor or one end of the switching element, and a first terminal of the switching element and a first output of the transformer are connected. Voltage superimposition means is connected between one end or the other end, and feedback control means for controlling the duty of the switching element is connected between the first output side of the transformer and the control terminal of the switching element. Features a power supply device. (2) The voltage superimposition means includes a diode, one end of which is connected to one end of the first output of the transformer, and a capacitor connected between the other end of the diode and the first terminal of the switching element. 2. The power supply device according to claim 1, further comprising a diode connected to the other end of the diode to serve as a first external output terminal. (3) The power supply device according to claim 1, wherein the voltage superimposition means comprises a rectifier circuit connected between the first terminal of the switching element and the other end of the first output of the transformer.